站长资讯网函数名: labs
功 能: 取长整型绝对值
用 法: long labs(long n);
程序例:
#include <stdio.h>
#include <math.h>
int main(void)
{
long result;
long x = -12345678L;
result= labs(x);
printf(“number: %ld abs value: %ldn”,
x, result);
return 0;
}
函数名: ldexp
功 能: 计算value*2的幂
用 法: double ldexp(double value, int exp);
程序例:
#include <stdio.h>
#include <math.h>
int main(void)
{
double value;
double x = 2;
/* ldexp raises 2 by a power of 3
then multiplies the result by 2 */
value = ldexp(x,3);
printf(“The ldexp value is: %lfn”,
value);
return 0;
}
函数名: ldiv
功 能: 两个长整型数相除, 返回商和余数
用 法: ldiv_t ldiv(long lnumer, long ldenom);
程序例:
/* ldiv example */
#include <stdlib.h>
#include <stdio.h>
int main(void)
{
ldiv_t lx;
lx = ldiv(100000L, 30000L);
printf(“100000 div 30000 = %ld remainder %ldn”, lx.quot, lx.rem);
return 0;
}
函数名: lfind
功 能: 执行线性搜索
用 法: void *lfind(void *key, void *base, int *nelem, int width,
int (*fcmp)());
程序例:
#include <stdio.h>
#include <stdlib.h>
int compare(int *x, int *y)
{
return( *x – *y );
}
int main(void)
{
int array[5] = {35, 87, 46, 99, 12};
size_t nelem = 5;
int key;
int *result;
key = 99;
result = lfind(&key, array, &nelem,
sizeof(int), (int(*)(const void *,const void *))compare);
if (result)
printf(“Number %d foundn”,key);
else
printf(“Number %d not foundn”,key);
return 0;
}
函数名: line
功 能: 在指定两点间画一直线
用 法: void far line(int x0, int y0, int x1, int y1);
程序例:
#include <graphics.h>
#include <stdlib.h>
#include <stdio.h>
#include <conio.h>
int main(void)
{
/* request auto detection */
int gdriver = DETECT, gmode, errorcode;
int xmax, ymax;
/* initialize graphics and local variables */
initgraph(&gdriver, &gmode, “”);
/* read result of initialization */
errorcode = graphresult();
/* an error occurred */
if (errorcode != grOk)
{
printf(“Graphics error: %sn”,
grapherrormsg(errorcode));
printf(“Press any key to halt:”);
getch();
exit(1);
}
setcolor(getmaxcolor());
xmax = getmaxx();
ymax = getmaxy();
/* draw a diagonal line */
line(0, 0, xmax, ymax);
/* clean up */
getch();
closegraph();
return 0;
}
函数名: linerel
功 能: 从当前位置点(CP)到与CP有一给定相对距离的点画一直线
用 法: void far linerel(int dx, int dy);
程序例:
#include <graphics.h>
#include <stdlib.h>
#include <stdio.h>
#include <conio.h>
int main(void)
{
/* request auto detection */
int gdriver = DETECT, gmode, errorcode;
char msg[80];
/* initialize graphics and local variables */
initgraph(&gdriver, &gmode, “”);
/* read result of initialization */
errorcode = graphresult();
if (errorcode != grOk)
{
printf(“Graphics error: %sn”,
grapherrormsg(errorcode));
printf(“Press any key to halt:”);
getch();
exit(1);
}
/* move the C.P. to location (20, 30) */
moveto(20, 30);
/* create and output a
message at (20, 30) */
sprintf(msg, ” (%d, %d)”, getx(), gety());
outtextxy(20, 30, msg);
/* draw a line to a point a relative
distance away from the current
value of C.P. */
linerel(100, 100);
/* create and output a message at C.P. */
sprintf(msg, ” (%d, %d)”, getx(), gety());
outtext(msg);
/* clean up */
getch();
closegraph();
return 0;
}
函数名: localtime
功 能: 把日期和时间转变为结构
用 法: struct tm *localtime(long *clock);
程序例:
#include <time.h>
#include <stdio.h>
#include <dos.h>
int main(void)
{
time_t timer;
struct tm *tblock;
/* gets time of day */
timer = time(NULL);
/* converts date/time to a structure */
tblock = localtime(&timer);
printf(“Local time is: %s”, asctime(tblock));
return 0;
}
函数名: lock
功 能: 设置文件共享锁
用 法: int lock(int handle, long offset, long length);
程序例:
#include <io.h>
#include <fcntl.h>
#include <sysstat.h>
#include <process.h>
#include <share.h>
#include <stdio.h>
int main(void)
{
int handle, status;
long length;
/* Must have DOS Share.exe loaded for */
/* file locking to function properly */
handle = sopen(“c:\autoexec.bat”,
O_RDONLY,SH_DENYNO,S_IREAD);
if (handle < 0)
{
printf(“sopen failedn”);
exit(1);
}
length = filelength(handle);
status = lock(handle,0L,length/2);
if (status == 0)
printf(“lock succeededn”);
else
printf(“lock failedn”);
status = unlock(handle,0L,length/2);
if (status == 0)
printf(“unlock succeededn”);
else
printf(“unlock failedn”);
close(handle);
return 0;
}
函数名: log
功 能: 对数函数ln(x)
用 法: double log(double x);
程序例:
#include <math.h>
#include <stdio.h>
int main(void)
{
double result;
double x = 8.6872;
result = log(x);
printf(“The natural log of %lf is %lfn”, x, result);
return 0;
}
函数名: log10
功 能: 对数函数log
用 法: double log10(double x);
程序例:
#include <math.h>
#include <stdio.h>
int main(void)
{
double result;
double x = 800.6872;
result = log10(x);
printf(“The common log of %lf is %lfn”, x, result);
return 0;
}
函数名: longjump
功 能: 执行非局部转移
用 法: void longjump(jmp_buf env, int val);
程序例:
#include <stdio.h>
#include <setjmp.h>
#include <stdlib.h>
void subroutine(jmp_buf);
int main(void)
{
int value;
jmp_buf jumper;
value = setjmp(jumper);
if (value != 0)
{
printf(“Longjmp with value %dn”, value);
exit(value);
}
printf(“About to call subroutine … n”);
subroutine(jumper);
return 0;
}
void subroutine(jmp_buf jumper)
{
longjmp(jumper,1);
}
函数名: lowvideo
功 能: 选择低亮度字符
用 法: void lowvideo(void);
程序例:
#include <conio.h>
int main(void)
{
clrscr();
highvideo();
cprintf(“High Intesity Textrn”);
lowvideo();
gotoxy(1,2);
cprintf(“Low Intensity Textrn”);
return 0;
}
函数名: lrotl, _lrotl
功 能: 将无符号长整型数向左循环移位
用 法: unsigned long lrotl(unsigned long lvalue, int count);
unsigned long _lrotl(unsigned long lvalue, int count);
程序例:
/* lrotl example */
#include <stdlib.h>
#include <stdio.h>
int main(void)
{
unsigned long result;
unsigned long value = 100;
result = _lrotl(value,1);
printf(“The value %lu rotated left one bit is: %lun”, value, result);
return 0;
}
函数名: lsearch
功 能: 线性搜索
用 法: void *lsearch(const void *key, void *base, size_t *nelem,
size_t width, int (*fcmp)(const void *, const void *));
程序例:
#include <stdio.h>
#include <stdlib.h>
int compare(int *x, int *y)
{
return( *x – *y );
}
int main(void)
{
int array[5] = {35, 87, 46, 99, 12};
size_t nelem = 5;
int key;
int *result;
key = 99;
result = lfind(&key, array, &nelem,
sizeof(int), (int(*)(const void *,const void *))compare);
if (result)
printf(“Number %d foundn”,key);
else
printf(“Number %d not foundn”,key);
return 0;
}
函数名: lseek
功 能: 移动文件读/写指针
用 法: long lseek(int handle, long offset, int fromwhere);
程序例:
#include <sysstat.h>
#include <string.h>
#include <stdio.h>
#include <fcntl.h>
#include <io.h>
int main(void)
{
int handle;
char msg[] = “This is a test”;
char ch;
/* create a file */
handle = open(“TEST.$$$”, O_CREAT | O_RDWR, S_IREAD | S_IWRITE);
/* write some data to the file */
write(handle, msg, strlen(msg));
/* seek to the begining of the file */
lseek(handle, 0L, SEEK_SET);
/* reads chars from the file until we hit EOF */
do
{
read(handle, &ch, 1);
printf(“%c”, ch);
} while (!eof(handle));
close(handle);
return 0;
}
